The present invention relates to a coating apparatus and a coating method for coating a substrate such as a glass substrate for liquid crystal display (LCD) and a semiconductor wafer, for example, with a treatment solution or the like such as a resist solution.
Conventionally, a method called xe2x80x9ca spin coating methodxe2x80x9d is generally used for coating a glass substrate for LCD (hereinafter the glass substrate for LCD is simply described as xe2x80x9ca glass substratexe2x80x9d) with treatment agent such as resist solution. In the spin coating method, a glass substrate is rotated at high speed within a horizontal surface, then a resist solution is dropped in the vicinity of the center of rotation to coat the entire glass substrate therewith by centrifugal force of the glass substrate, and excess resist solution is spun off and eliminated by centrifugal force to make a coating film thinner.
According to the spin coating method, the advantage of enabling coating with a coating apparatus comparatively simple in structure is obtained, but since a resist solution is spread on the entire glass substrate, even a portion with no need for coating is coated with the resist solution, therefore causing the disadvantage of requiring a larger amount of resist solution compared to the area requiring resist coating.
There is a requirement for a thinner resist coating film following an increase in the integration of semiconductor devices formed on a substrate, but in the spin coating method, thickness of the resist coating film is determined according to the viscosity of the resist solution dropped and the rotational speed of the glass substrate, and therefore the thinness of the coating film has limitations.
Consequently, various kinds of proposals have been made to eliminate the disadvantages of the spin coating method.
The prior art, for example, Japanese Patent Application Laid-open No. 4-118073 discloses xe2x80x9ca coating apparatus having a slot for discharging coating material on a coating surface of a work piece to be coated, including a slot coater moved relatively to the work piece in a direction perpendicular to the direction in which the slot is extended, and a spin type coating film adjusting mechanism provided at the slot coater and rotating the work piece coated with coating material on the coating surface at high speed while holding it so that the coating surface is almost horizontalxe2x80x9d.
According to the above method, coating is effectively made with a small amount of coating material.
However, the aforesaid coating apparatus has the following disadvantages.
Specifically, when the space between a slot and a work piece (substrate) varies, the thickness of coating film varies, and the thickness of coating film discharged differs between the center and the end portions of the slot, therefore there is the disadvantage that a highly precise control is needed in order that the space between the slot and substrate is made smaller and constant.
In addition, in the coating apparatus, coating material is discharged in a liquid film state from the slot toward the work piece, therefore it is necessary to use coating material with viscosity high to some extent in order to form the liquid film. A solution with comparatively high viscosity as described above is easy to dry, therefore resulting in the disadvantage of easily causing the slot to clog.
Further, liquid with comparatively high viscosity like the above coating material has a lower content of solvent and the viscosity is easily varied, therefore causing the disadvantage of requiring highly precise control of viscosity.
In addition, in order to make a thin film of coating material with high viscosity discharged on the surface of a work piece and to make the film thickness uniform by rotation, rotation at higher speed is required. However, it is difficult to rotate a LCD with a large screen at high speed, therefore causing the disadvantage that the apparatus is not applicable to a large LCD.
Further, when rotated with coating material with high viscosity, excess coating material is spun off by centrifugal force, and adheres to the inner wall of a rotor cup, but there is the disadvantage that this coating material is difficult to eliminate because of high viscosity.
Furthermore, a large continuous opening is necessary as an opening for forming the slot, therefore causing the disadvantage of a die head increasing in size out of necessity to maintain the strength of dies.
An object of the present invention is to provide a coating apparatus and coating method which loosen the requirements for mechanical and operational accuracy such as the space between a nozzle and a substrate.
Another object of the present invention is to provide a coating apparatus and method in which treatment agent with low viscosity can be used.
In a first aspect of the present invention, an operation of supplying a treatment agent, and an operation of thin film making of the treatment agent are separately performed, and while the treatment agent is supplied with treatment supplying means, thin film making of the treatment agent is performed with thin film making means. As a result, requirements of mechanical accuracy and operational accuracy for the step of each of the aforementioned operations are relaxed.
Specifically, it is not necessary to control the shapes and the sizes of the nozzles, a space between the treatment agent nozzle and the substrate to be treated, and the like as strictly as in the aforesaid continuous slot.
A treatment agent is supplied onto the surface of the substrate to be treated at a plurality of positions, and therefore a treatment agent with comparatively lower viscosity can be used. Consequently, the treatment agent is difficult to dry with a high content of solvent, therefore making it difficult to clog the nozzles.
Further, the viscosity of the treatment agent has less effect on the film thickness, therefore making it easy to control the viscosity of the treatment agent.
In addition, since a treatment agent with low viscosity can be used, when thin film making is performed by rotating the treatment agent after the coating operation, the coating film can be made thinner at low rpm, therefore making it applicable to a large LCD substrate.
Further, with low viscosity, the treatment agent is easy to remove even if it is attached on the rotor cup.
Furthermore, the treatment agent is supplied separately at a plurality of positions, therefore making it unnecessary to use a treatment agent nozzle including a large opening as a slot, and preventing the treatment agent nozzle increasing in size.
In addition, since thin film making is achieved by being rotated in an enclosed state, airflow is not disturbed, and a coating film with uniform thickness can be obtained.
Further, in another aspect of the present invention, as thin film making means, means for oscillating the treated substrate is employed, therefore enabling thin film making with reliability in a simple construction.
It should be noted that xe2x80x9coscillationxe2x80x9d described here includes a vibration in a linear direction with use of an actuator (vibrating element) or the like, and an angular vibration of a spin chuck by normal and reverse rotation in a range of a minute angle in a short cycle. Further, means for rotating the treated substrate is employed as thin film making means, thereby enabling thin film making with reliability in a simple construction.
For example, if the spin chuck is used, a conventional type of apparatus can be used, and it is not necessary to add a new component or element, therefore eliminating a need for new investment in equipment, thus almost eliminating an increase in manufacturing cost.
When using a spin chuck, it is possible to spin off and remove an excess treatment agent by rotating the spin chuck at high speed after making oscillation by an angular vibration within a minute angle after coating the treatment agent.
In still another aspect of the invention, the treatment agents supplied adjacently to one another are supplied at such intervals that the treatment agents integrate with one another on the surface of the treated substrate by the aforesaid thin film making means. As a result, the treatment agents supplied onto the treated substrate are surely integrated, therefore forming a coating film with uniform and smaller thickness much more reliably.
By means for previously supplying solvent onto the surface of the substrate to be treated before a treatment agent is supplied, the surface of the substrate to be treated is previously made wet with solvent by supplying the solvent, thereby increasing comformability of the treatment agent with the substrate to be treated, and quickly spreading the treatment agent, which runs on the surface of the substrate to be treated with the solvent layer between them, therefore surely making the coating film uniform.
In yet another aspect of the invention, a standby position is provided adjacently to the holding member or the spin chuck, and the pressure sensor is placed on the surface of the standby position, opposing the aforesaid treatment agent nozzles to detect the discharge pressure of each treatment agent nozzle. A monitoring section for monitoring the operational condition of each of the aforesaid treatment nozzles based on the detected discharge pressure is provided, and therefore the operational condition of each treatment agent nozzle can be always monitored with the monitoring section, and the treatment agent nozzle clogged is discovered as quickly as possible if any one of the treatment agent nozzles are clogged, which prevents the production from proceeding with a problem occurring to the treatment agent nozzle, therefore slowdown in production is eliminated, and manufacturing efficiency and cost are improved.
An operation of supplying a treatment agent, and an operation of thin film making of the treatment agent are separately performed, and while the treatment agent is supplied with treatment supplying means, thin film making of the treatment agent is performed with thin film making means, therefore relaxing requirements of mechanical accuracy and operational accuracy for the step of each of the aforementioned operations.
A treatment agent is supplied onto the surface of the substrate to be treated at a plurality of positions, and therefore a treatment agent with comparatively lower viscosity can be used. Consequently, the treatment agent is difficult to dry with a high content of solvent, therefore reducing clogging of the nozzles.
Further, the viscosity of the treatment agent has less effect on the film thickness, therefore making it easy to control the viscosity of the treatment agent.
In addition, since a treatment agent with low viscosity can be used, when thin film making is performed by rotating the treatment agent after treatment, the coating film can be made thinner at low rpm, therefore making it applicable to a large LCD substrate.
Further, with low viscosity, the treatment agent is easy to remove even if it is attached on the rotor cup.
Furthermore, the treatment agent is supplied separately at a plurality of positions, therefore making it unnecessary to use a treatment agent nozzle including a large opening as a slot, and preventing the treatment agent nozzle from increasing in size.
In addition, since thin film making is performed by being rotated in an enclosed state, airflow is not disturbed, and a coating film with uniform thickness can be obtained.